The present invention relates generally to safety device for cameras, and more particularly pertains to an improved device for preventing double exposure to cameras which are adapted for use with film perforated at predetermined metering intervals.
Cameras are known in which a sensing pawl is moved a small amount by the camera loaded film after engaging a metering perforation in the film, to prevent further transportation of the film as well as to disable the double exposure prevention mechanism so that mechanical shutter release operation is allowed. It is also known with such cameras, as for example that is described in U.S. Pat. No. 3,820,142, that the double exposure prevention mechanism may be disabled when a film or film cartridge is not loaded in the camera so that the shutter may be operated without film for test purposes for the demonstration of the camera operation before customers.
Such cameras are usually of small size and light weight which is desirable for carrying purposes but which sometimes produces a blurred picture due to camera movement during the picture taking operation when the camera is supported by hand. Hence it is desirable if such cameras are provided with an electromagnetic shutter release device which requires a short stroke for the shutter release operation and reduces the possibility of blurred picture. The electromagnetic shutter release mechanism may serve as a battery checker if the power source battery for exposure control is also used for the mechanism.